Bladed fluid machine for increasing the pressure of a fluid



Oct. 11, 1960 E. A. STALKER 2,955,746

BLADED FLUID MACHINE FOR INCREASING THE PRESSURE OF A FLUID Filed May 24, 1954 IN VEN TOR.

QMMMM United States Patent Ofiice 2,955,?45 Patented Oct. 11, 1960 BLADED FLUID MACHINE FOR INCREASING THE PRESSURE OF A FLUID Edward A. Stalker, 406 N. Farragut St., Bay City, Mich. Filed May 24, 1954, Ser. No. 431,758

12 Claims. (Cl. 230-120) This invention relates to compressors, blowers, and the like herein referred to as compressors.

An object of the invention is to provide a radial diffusion compressor of high efliciency over a wide range of volume flow per revolution with the flow discharged transversely to the axis of rotation;

Another object is to provide a compressor having sheet stock blades for economical fabrication.

Still another object is to provide a compressor for creating a large static pressure rise and a large range of volume flow per revolution at high efficiency.

Other objects will appear from the description drawings and claims.

The above objects are accomplished by the means illustrated in the accompanying drawings in which- Fig. l is an axial section through a compressor according to this invention representing a preferred form thereof;

Fig. 2 is a front view of the compressor of Fig. 1;

Fig. 3 is a fragmentary development of the blading of the rotor and the guide vanes;

Fig. 4 is a diagram of the fluid flow vectors pertaining to the inlet guide vanes and the rotor blades of this invention;

Fig. 5 is a diagram of fluid flow theory;

Fig. 6 is a graph of pressure rise in the pumped fluid versus volume of flow per revolution;

Fig. 7 is a tip view of a rotor blade;

Fig. 8 is a chordwise section through a rotor blade at the root end thereof; and

Fig. 9 shows an alternate blade section for a rotor.

In this invention the blades of the rotor have rotor flow passages between them which preferably expand greatly in cross sectional area and in radial depth so that a large static pressure rise occurs in these passages and the component of axial velocity is small. Then the direction of flow coming from the rotor is very closely along the plane of rotation, providing for its discharge in a direction transverse to the direction of the axis of rotation. However it is desirable that the static pressure does not build up to too great an extent toward the tips of the blades. The rotation of a rotor tends to cause a large centrifugal pressure near the tips of the blades arising from centrifugal action on the radially extending column of fluid between the blades, especially that portion of the column adjacent to the rear end of the rotor. This pressure, if allowed to exist, would cause a reduction in flow through the rotor.

In this invention provision is made to offset the undesirable features which would result from a large static pressure rise in the rotor and the counter whirl in the inlet guide vanes by shaping the guiding surfaces of the case and rotor to provide a negative centrifugal pressure, that is one acting radially inward.

The combination of counter rotation inlet guide vanes and rotor configuration provides for the discharge of the flow of fluid with high efliciency and pressure over a wide range of volume flow per revolution.

vectors relating to Referring now to the drawings, the compressor is indicated generally as 10 in Figs. 1 and 2. It has the case means 11 comprised of the rotor case 12, the inlet duct 14, and the exit duct 16. The rotor 18 is mounted on theshaft 20 supported in the bearing 22. The rotor hub 28 carries the rotor blades 30 peripherally spaced about the rim 34. The rotor hub defines with the rotor case an annular flow channel 31 which conducts the main flow through the compressor and into exit duct 33. The blades are contoured to the inside surface of the case and preferably conform to this surface along substantially their whole tip length.

The rotor blades have the rotor flow passages 40 between them and are shaped to give a large dilfusion ratio to these passages. With a large diffusion ratio the relative velocity at the exit of each passage is small compared to the velocity at the corresponding inlet. Thenthe flow leaving the rotor has a very small axial component of velocity and the direction of the absolute velocity makes a small angle with the plane of rotation.

As shown in Fig. 7 the blades 30 have a very large curvature in their root sections 42 and substantially less curvature at their tip sections 44. Because of the curvature in the blades and their increasing radial depth rearward the cross sectional widths of the passages increase rearward, that is downstream, so that each exit cross sectional area A is much larger than the corresponding inlet cross sectional area A The diffusion ratio is the ratio of A to A Preferably this should be of the order of 1.3 or more preferably about 2. The ratio of radial depths of the exits to the inlets should be greater than 1.15.

When the rotor is rotated fluid enters the compressor inlet opening 60, Fig. l and flows through the inlet guide vanes 62 into the rotor passages 40. In the rotor the centrifugal pressure due to rotation about the axis tends to create a substantial static pressure rise in the region of the blade tips in addition to the rise due to diffusion. Because of the resulting balance of pressures and energies along the radius or span of the blades the mass flow through the rotor at the tip ends of the blades will be much smaller than at the root ends. This is undesirable with respect to the efliciency of the rotor.

In this invention the mass flow through the rotor in the neighborhood of the blade tips is increased by creating a pressure to offset, at least in part, the centrifugal pressure arising from the rotation of the rotor. This is accomplished in part by giving the inlet duct a negative curvature about one or more centers lying away from the axis of rotation. In Fig. l the radius of curvature R of the center line 70 of the passage is curved in axial planes to be convex to the axis of rotation and has its center at 72 on the far side of this center line from the axis of rotation of shaft 20.

The hub rim converges axially downstream toward the axis of rotation and produces fluid pressure acting radially inward in opposition to the centrifugal pressure arising from rotation of the fluid in the rotor about its axis. Preferably the hub rim is concave with the exit end of the rim nearer the axis of rotation than the inlet end of the rim.

When the pumped fluid is drawn into the inlet duct a negative centrifugal pressure is created acting toward the axis of rotation, that is in opposition to the centrifugal pressure from the rotation about the shaft axis. Due to the inertia ofthe fluid this negative centrifugal pressure can persist into the rotor and reinforce the negative centrifugal pressure from the curvature of the hub n'm. These pressures influence the flow leaving the rotor. I

When the centrifugal pressure from rotor rotation is offset at least in part by the negative centrifugal press sure arising from negative curvature of the flow in axial planes, more fluid flows through the rotor at the outer ends or tips of the blades. This is particularly important where the radial depth of the passage is larger at the 'exit than at the inlet because of the added diffusion. This increases the efficiency of the rotor. l The efliciency of the rotor is f there is a greater'pressure rise near the root ends of the blades, i.e., away from the case and from the gaps between the blade tips and the case. V Besides improving the flow through the rotor, the curved inlet surfaces of the case means also improve the action of the inlet guide vanes 62 which are also designed to'cause a rotation of the 'fluid'about the shaft axis. This is discussed further subsequently. j 7

In order to achieve a very high total head pressure creasedin part because ratio the rotor blades, Figs. 3, 7 and 8, preferably have large portions thereof curved chordwise so that their aft ends 64 are directed more nearly parallel to the axis of rotation (axis of shaft than to the direction of the nose portion 66 or ahead of the axis referred to the direction of rotation 65. Thecurvature and the increasing radial depths increase the cross sectional areas of the exits of the rotor passages relative to their inlet areas which difluses the fluid flow and increases the density of the fluid in the rotor passages. In turn this tends to increase the rotational centrifugal pressure in the rotor adjacent to the blade tips which as remarked earlier is undesirable. Consequently an inlet duct curvature to oppose the rotor-rotational centrifugal'pressure becomes very significant with curved blades and particularly so with curved blades of large solidity at their root ends, since the closer the blades are spaced the greater effect the blades have on the fluid flowing between them. Also the greater the radial depth the greater the outward centrifugal pressure.

The blades are preferably placed close together to achieve a solidity greater thanabout one at the mean line 70 and preferably greater than 2 and less than 10. It is also preferable that the leading edge of the following blade of a. pair of rotor blades be chordwise forward of about the mid point of the chord of the leading blade.

. 4 the vanes may be represented by 90. Then the flow vector relative to the segments of the rotor blades will be 92 and the change in angle of incidence of each segment will be A04 If vanes were employed which gave no whirl to the fluid the vector for fluid leaving the vanes would be 100 (Fig. 4) equal to the axial'velocity component 102 of vector 82. For the same peripheral component 84 the relative velocity'is 103. if the volume of the flow is decreased by the new relative vector is 106 making the change in angle of incidence A0121 p A comparison in Fig. r4 of the changes in angle of incidence,'Aa with Au shows that with backward curved vanes the-change in angle of incidence is only about one-half of the change for zero backward curvature which would give no whirl to the fluid leaving the vanes. This relationship can also be shown by calculation-of the changes in angle of incidence. "Q

As shown in Fig. 5 the peripheral component of the velocity of the fluid leaving the inlet guide vanes can be expressed as k times U. The axial component can be expressed as k U. #1 is the angle between the flow vector from the inlet guide vanes andthe plane of rotation. is the angle between the relative vector 86, Fig. 8 and the plane of rotation. Then tan 1,0

and

i k1 U tan kZU whence fl v tan :;5 2 tan b (5) Also from Fig. 4 it is seen that All [3 47 With the blades close together it is desirable to make Q I the blades thin and with blade sections of constant thickness throughout substantially their whole chordwise length to exclude constricting throats in the passages between the blades. the selection of sheet rock blades with their low costs of fabrication.

The radially inward divergence of the rim 34 serves to control the rate of diffusion of the flow along the root portions of the blades.

The smaller the pitch angle ,8 (measured between the tangent 142 to the mean camber line and the plane of rotation) the smaller is the angle 6 (Figs. 7 and 8) through which the blade can be curved. 0 is'the turning angle between the tangents to the mean camber line at the leading and trailing edges, 142 and 141 respectively, Fig. 7.

In order to extend the range of volume flow per revolution of the rotor, the inlet guide vanes 62 (Fig. 3)

are curved backward relative to the direction of rotation of the rotor 18. Thus 'the vanes deflect or rotate the flow of fluid coming through their passages 80 in a peripheral direction counter to the direction of rotation of the rotor blades 30. p

In Figs. 3 and 4 the flow vector aft of the inlet guide vanes is 82 when the compressor is passing 100% of the mass flow for which it is designed. The peripheral velocity of segments of the rotor blades at a selected radius is 84 or U, and the flow vector relative to the segments is then 86. through the compressor is decreased 50% as it may be in the course of its use the vector of the flow leaving it for instance the volume of flow These considerations also lead to Y r TableI shows the changes in angle of incidence 0: for the compressor with counter whirl vanes and 0: for vanes providing'axial flow; These are calculated according to Equations l-4. In each case the axial velocities at the selected conditions are equal and k =k The axial velocities are proportionalto k since the peripheral velocity'U is the same in both cases.

It is clear from this table that the counter whirl inlet vanes greatly reduce the changes in angle of incidence. 7 It can also be shown for a small value of 5 that a remains substantially constant and small for a wide variation in axial velocity which determines the magniture of the volume of flow through the compressor.

By using the backward curved vanes in proper relation to the other geometric variables the axial flow rotor is made to function over a wide range of volume flow with a sufiiciently small variation in angle of incidence to preclude separation of the flow from theblade surfaces. This insures high pressure rises and high efficiency over the useful range of operation.

It may be deduced from theequations that the smaller the angle #1 the less variation there will be in the angle of incidence a for a given percentage variation in the axial velocity which determines the volume flow. Ac-

cordingly it is desirable for the best results to make 1,0

less than about and pitch angle 5 less than about 35 If it is desired to sustain a high pressure rise substantially to the condition of zero volume flow, the pitch angle ,8 may be made about equal to the stall angle of incidence of the blades, that is about 12 degrees, or less. This is the angle of incidence at which the flow separates from the convex side of the blade.

Since the counterflow inlet guide vanes limit the range of angles of incidence required by the blades of the rotor the latter can be made of thin sheet metal and function with high efficiency over a large range of operation.

The flow leaves the rotor with the relative velocity 110. See Fig. 3. The peripheral velocity of the rotor blade is 112, the velocity relative to the stator beingshown at 114. It will thus be seen that the discharge from the flow passages is directed primarily transversely of the axis and thus directly into the exit duct 33 extending generally in the same direction. This assures that the flow will be properly received within the exit duct without the presence of guide vanes in the exit duct, thus avoiding the obstructing effects of such vanes with their accompanying volume range limitation.

The preferred magnitude of the radius R of the curvature of the center line 79 is related to the pitch angle 5 of the rotor blades at the center line 70.

The outward centrifugal pressure at the mean line 70 due to the rotation of the rotor about the rotor axis is closely where p is the mass density of the fluid, U is the periphcral velocity at center line 70 and r is the radius to this center line.

As shown in Fig. 4 the axial velocity entering the rotor passages is U tan 5. The inward centrifugal pressure at the mean or center line 76 due to curvature of the flow at radius R is then closely P( 1 tallz B R (5) These two pressures should be equal. That is whence R=r(l+k tan 5 (7) Some variation on either side of this value of R will still produce improved performance. The radius R should lie between the limits Preferably the radii R of the outer case 12 should be equal to the radius R to the mean line 70 reduced by one-half the blade span. However it may be less than R by greater amounts.

The radius R to the concave surface of the hub rim should be equal to R plus one-half the blade span. The centers of the various radii need not coincide When the blades have a thin constant thickness blade section such as sheet metal provides, the range of volume flow per revolution tends to be limited by these characteristics. It is especially important then with this type of blade section to employ means to extend the range of the rotor blades. In this invention this is accomplished in part by the use of the counter flow guide vanes and the negative curvature in the passages of the inlet and rotor as already described.

An enlarged root section of the rotor blade 3% is shown in Fig. 8 of the preferred cross sectional shape. It has a mean camber line 140 which is preferably curved more along the rear part. Angles of incidence a are to be referred to the tangent 142 to the mean camand her line at the center 144 of the nose radius and the relative flow vector 92.

For economy of construction and to facilitate close peripheral spacing of the blades they are preferably made with blade sections of substantially constant thickness from substantially the leading edge to the trailing edge. As shown in Fig. 8 each blade has a constant thickness chordwise with faired nose and tail portions. These portions extend inward from the blade edges by one or more times the blade thickness and are preferably limited to a small length equal to only several times the blade thickness.

The blades may also be of varying thickness with front and rear portions tapering from a locality of maximum thickness fore and aft respectively to the leading and trailing edges as shown in blade 146 in Fig. 9.

The forward portions of the blades are preferably directed more nearly parallel to the plane of rotation 147 (see Fig. 8) than normal thereto, as determined by the direction of the tangent to the mean camber line of the fore portion relative to the plane of rotation. Preferably the aft portion, as determined by its tangent to its mean camber line is more nearly parallel to the axis of rotor rotation htan to the fore portion of the blade.

The machines of this invention are for use in moving large volumes of elastic fluid against substantial back pressures. Accordingly the tips of the blades fit closely to and conform to the contours of the surface of the case adjacent to them.

Furthermore the ratio of the maximum radius of the hub to the radius of the blade tips at the inlets of the rotor passages is preferably greater than 0.5 and in the range of 0.5 to 0.7 to preclude back-flow in the region adjacent to the blade roots. The blade roots are highly cambered to serve this same purpose.

The passages between the rotor blades can have a large ratio of exit to inlet cross sectional area. This is achieved by a greater radial depth at the exit than at the inlet and preferably also by curving the blades along the chord direction.

The increasing radial depth particularly tends to induce a large diffusion of the flow in the vicinity of the case and a corresponding increase in the static pressure. Also the centrifugal pressure arising from the rotation of the fluid, imparted by the rotor blades tends to augment the static pressure from the diffusion. Furthermore the flow in an axial plane along the case is convex causing an increment or" centrifugal pressure acting radially outward. These pressures tend to reduce the volume of flow through the outer portions of the channel between the hub and the case.

A reduction in volume of flow is very disadvantageous.

Effects of high pressures at the fluid tips also would extend upstream and adversely aflect the angles of incidence of the rotor blades.

In order to improve and extend the operational range of angles of incidence of the rotor blades, inlet guide vanes are provided to give the fluid flow a pre-Whirl counter to the direction of the rotor. However such a pre-whirl sets up centrifugal pressure toward the outer ends of the vanes tending to limit the volume of flow.

For low cost it is desirable to make the blades of sheet stock like sheet metal. Such blades tend to have a limited useful range of angles of incidence tending to limit the volume flow per revolution of the rotor.

In order to establish the angles of incidence and the volume flow per revolution at desirable values the walls of the case means are curved in axial planes to be convex to the axis of rotation to give a centrifugal pressure acting toward the axis of rotation of the rotor to oppose the rotational centrifugal and other pressures in the region of the rotor blade tips and the outer portions of the vane flow passages 3!). The effect of the centrifugal pressure quired for a large increase in the volume flow. The case means also cooperates with the inlet guide to reduce or oppose their tendency to build up an undesirable magnitude of centrifugal pressure at their outer ends. Thus the case means, rotor, and inlet guide vanes cooperate to produce a large volume flow and a large range of volume flow per revolution' of the rotor. They also cooperate with the blades so that they may be made cheaply from sheet stock and still provide a large range of volume flow per revolution;

' It is desirable to have a graph of pressure rise AP versus volume flow per revolution V like 150m Fig. 6. If as shown the curve has everywhere a negative slope the operation of the compressor will be stable. That is it will exclude surging. The curve preferably should be at least horizontal as shown by 152 although some positive slope in some installations can be tolerated particularly near the end ofthe curve for very small volume of flow. To achieve a satisfactory curve close to the condition of zero flow the pitch angle is preferably less than about 16. j The compressor of this invention is of the axial flow type'characterized by rotor flow passages extending in the general radial direction to an exit facing in the general axial direction for discharging fluid in the general axial direction. As viewed in the axial direction the exit and inlet of each rotor passage overlaps substantially.

It will now be clear that I have disclosed a unique 'machine for efficiently increasing the pressure of a fluid to relatively large values while providing a wide range of volume flow per revolution.

While I have illustrated a specific. form in this invention it is to be understood that I do not intend to limit myself to this exact form but intend'to claim my inven tion broadly as indicated by the appended claims.

I claim:

1. In combination in a compressor for raisingthe'pressure of an elastic fluid, a. case means comprising an inlet duct, 'arotor case and an exit duct, a rotor hub mounted in saidrotor case for rotation about an axis and defining a flow channel with said rotor case, said channel registering with said inlet and exit ducts vto conduct a flow of fluid, said exit duct being constructed to discharge said *fluid transversely to said axis, and a plurality of peripherally spaced axial flow blades carried on said hub withrotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with "a greater cross sectional area and radial depth at its exitthan at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, a plurality of guide vanes positioned in said inlet duct upstream adjacent to said rotor, said vanes having flow passages therebetween and being curved backward so that the tangent to the mean camber line at the rear end of each said vane makes an angle with the plane ofrotation less than 65 degrees to direct said fluid counter to the direction of rotation, said rotor blades being angularly positioned on said hub at a pitch angle less than 35 degrees to cooperate with said guide vanes in establishing an extended range of volume flow per revolution.

2. In combination in a compressor for raising the pressure of an elastic fluid, a case means comprising an inlet duct, a rotor case and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and defining a flow channel with said rotorcase, said channelregister- '8 ingiwith said inlet and exit'ducts to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely 'to said axis, and a plurality of peripherallyspaced axial flow blades carried on said hub with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with "a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of saidaxis and into said exit duct generally in the line therewith, a plurality of axial flow guide vanes positioned in said inlet duct upstream adjacent to said rotor, said vanes having vane sections of substantially parallel sides extending between faired leading and trailing edges, said vanes being positioned so that the-tangent to the mean camber line at the rear end of each said vane makes an angle with the plane of rotation to direct said fluid counter to the direction of rotation, said rotor blades being angularly positioned on said hub at a pitch angle less than 16 degrees to cooperate with said guide vanes in establishing an extended range of volume flow per revolution, each said rotor blade'having blade sections of substantially vparallel sides extending between faired leading and trailing ledges along major portions of the chord lengths of said blades.

3. In combination in a compressor for raising the pressure of an elastic fluid, a case means comprising an inlet duct, a rotor case and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and defining a flow channel-with said rotor case, said channel registering with said inlet and exit ducts to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, and a plurality of peripherallyspaced axial flow blades carried on said hub with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity or" flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, a plurality of axial flow guide vanes positioned in said inlet duct upstream adjacent to said rotor with guide vane passages between said vanes, said vanes being positioned to direct fluid counter to the direction of rotation of said rotor blades, said inlet duct having its mean line curved in axial planes to be convex to said axis of rotation for producing a centrifugal pressure in said fluid toward said axis in said guide vane passages, said rotor blades and said guide vanes cooperating with said inlet duct topump a large range of volume of fluid through said compressor with a limited range of angles of incidence for said rotor blades.

4. In combination in a compressor having a rotor and a stator for raising the pressure of an elastic fluid, a case means comprising an inlet duct, a rotor case and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and defining a flow channel with said rotor case, said channel registering with said inlet and exit ducts to conduct a flow of fluid, said exit duct being constructed todischarge said fluid transversely to said axis, and a plurality of peripherally spaced axial flow blades carried on said hub with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than'at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, said blades tending to cause an increase in static and centrifugal pressure at their tip ends during rotation thereof tending-to limit the range of volume flow of said fluid, said stator comprised ofta pluralityof axial flow guide vanes positionedin said inlet duct upstream adjacent to said rotor, said vanes having flow passages therebetween for said fluid and being positioned to direct said fluid counter to the direction of rotation of said rotor blades producing centrifugal pressure in said vane flow passages, each said stator and rotor having a hub to tip ratio at the inlets of said rotor passages in the range of 0.5 to 0.79 also tending to reduce the volume or" fluid flowing through the radially outer portions of said passages between said vanes and between said blades, said inlet duct having its mean line curved in axial planes to be convex to said axis of rotation for producing a centrifugal pressure in said fluid toward said axis in said guide vane passages to counteract said tendency to restrict said flow, said rotor blades and said guide vanes cooperating with said inlet duct to pump a large'range of volume of fluid through said compressor with a limited range of angles of incidence for said rotor blades.

5. In combination in a compressor for raising the pressure of an elastic fluid, a case means comprising an inlet duct, a rotor case and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis defining a flow channel with said rotor case, said channel registering with said inlet and exit ducts to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, a plurality of peripherally spaced axial flow blades carried on said hub with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, said blades having a solidity at the mean radius thereof greater than about 2, a plurality of guide vanes positioned in said inlet duct upstream from said rotor, said vanes having flow passages therebetween and being positioned to direct said fluid counter to the direction of rotation, each said rotor blade having a fore portion positioned at a substantial angle relative to said axis and an aft portion having curvature chordwise to be more nearly parallel to said axis than to said fore portion, said rotor having a hub ratio in the range from 0.5 to 0.7 tending with said curvature and said radial depth at said exit to excessively increase the centrifugal pressure in the neighborhood of the tips or" said rotor blades due to rotation of said rotor, said inlet duct being curved in axial planes convexly to said axis and having mean lines curved in axial planes for producing a centrifugal pressure in said fluid toward said axis persisting into said rotor passages by inertia of said fluid for opposing said rotor-rotational centrifugal pressure whereby said vanes and inlet duct cooperate with said rotor to provide a large range of volume flow through said compressor.

6. In combination in a compressor for raising the pres sure of an elastic fluid, a case means comprising an inlet duct, a rotor case and an inlet duct, a rotor hub mounted in said rotor case for rotation about an axis defining a flow channel with said rotor case, said channel registering with said inlet and exit ducts to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, a plurality of peripherally spaced axial flow blades carried on said hub defining a rotor with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge trom said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, said blades having a solidity at the mean radius thereof greater than about 2, a plurality of curved guide vanes positioned in said inlet duct upstream from said rotor, said vanes having constant thickness chord-wise along flow passages therebetween and being positioned to direct said fluid counter to the direction of rotation, each said rotor blade having a tore portion positioned at a pitch angle less than about 20 degrees, said rotor with said passages of sad radial depths tending with said blade curvature to excessively increase the centrifugal pressure in the neighborhood of the tips of said rotor blades due to rotation of said rotor, said inlet duct being curved in axial planes convexly to said axis and having mean lines curved in axial planes for producing a centrifugal pressure toward said axis persisting into said rotor passages due to fluid inertia for opposing said rotor-rotational centrifugal pressure whereby said vanes and inlet. duct cooperate with said rotor to provide a large range of volume flow through said compressor.

7. In combination in a compressor for raising the pressure of an elastic fluid, a case means defining an inlet duct, a rotor case, and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and defining a flow channel with said rotor case, said channelregistering with said inlet duct and said exit duct to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, a plurality of peripherally spaced axial flow blades carried on said hub defining a rotor with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, said blades being of sheet stock defining blade sections or" constant thickness chordwise along substantially the whole chord length tending withsaid radial depths to limit the range of volume flow of said fluid, and a plura-lity of curved vanes positioned in said inlet case upstream adjacent to said,rotor, said vanes being positioned to direct fluid toward said rotor blades counter to their direction of rotation, said vanes tending to cause an increase in static pressure away from said axis toward the tip ends of said vanes by centrifugal action which tends to limit the range or" volume flow of said fluid, saidinlet duct having a negatively curved wall at said vanes convex to said axis and a mean line curved in an axial plane to create a centrifugal pressure .in said fluid toward said axis cooperating with said vanes to extend the range of fluid volume flow through said rotor.

8. In combination in a compressor for raising the pressure of an elastic fluid, a case means defining an inlet duct, a rotor case, and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and defining a flow channel with said rotor case, said channel registering with said inlet duct and said exit duct to conduct a flow of fluid, said exit duct being const-ructed to discharge said fluid transversely to said axis, a plurality of peripherally spaced axial flow blades carried on said hub with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, said blades being of sheet stock defining blade sections of substanially the whole chord length thereof, said blades having their fore portions directed more nearly along the plane of rotation than normal thereto and having their rear portions directed more nearly along said axis than along said fore portions, said blade sections tending to limit the range of volume flowof said fluid, a plurality of curved vanes positioned in said inlet case upstream adjacent to said rotor, said vanes being positioned to direct fluid toward aces-me said rotor blades counter to their directionof rotation, said vanes tending to cause an increase in static pressure away from said axis toward the tip ends of said vanes by'centrifugalaction which tends to limit the range of volume flow of said fluid, said inlet duct having at said vanesconvex to said axis curved walls and a mean line curved in an axial plane to create'a centrifugal pressure in said, fluid toward said axis to oppose said increase in static pressure at said vane tip, said walls and said vanes cooperating with said rotor to extend the range of volume flow of said fluid through said rotor.

9. In combination in a compressor for raising the pressureof an elastic fluid, a case means defining an inlet duct, a rotor case, and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and defining a flow channel with said rotor case, said channel registering with said inlet duct and said exit duct to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, a plurality of peripherally spaced axial flow blades carried on said hub defining a rotor with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line therewith, said, blades being of sheet stock defining blade sections of constant thickness chordwise along substantially the whole chord length thereof, each 'said following blade of a pair having its leading edge upstream of about the mid point of the chord of the leading blade of said pair, said blades being curved chordwise to define with said radial depths a cross sectional area at the exit, of each said passage greater than about 1.3 times the cross sectional area at the inlet thereof to increase thestatic pressure of said fluid therein and direct said fluid irom said rotor chiefly in a peripheral direction in said exit duct, said blades tending to limit the range of volume flow of said fluid, a plurality of curved vanes positioned in said inlet case upstream adjacent to said rotor, said vanes being positioned to direct fluid toward said rotor blades counter to their direction of rotation, said vanes tending to cause an increase in static pressure awayfrom said axis toward the tip ends of said vanes by centrifugal action which tends to limit the range of volume flow of said fluid, said inlet duct having negatively curved walls convex to said axis at said vanes and mean lines curved in axial planes to create a centrifugal pressure in said fluid toward said axis, said walls and said vanes cooperating with said rotor to extend the range of vol ume flow of said fluid through said rotor.

l0. In combination in a compressor for raising the pressure of an elastic fluid, a case means defining an inlet duct, a rotor case, and an exit duct, a rotor' hub mounted in said rotor case for rotation about an axis and defining a flow channel with said rotor case, said channel registering with said inlet duct and said exit duct tor-conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, a plurality of peripherally spaced axial flow blades carried on said hub defining a rotor with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally inline therewith, said blades being curved chordwise to define with said radial depths a cross sectional area at the exit of each said passage greater than 1.3 times the cross sectional area at the inlet thereof to increase the static pressure of said fluid therein and tending to limit the range ofrvolu me flow through said rotor passages "near the outer ends of said blades thereof, said hub having a concave rim for establishing a centrifugal pressure acting toward said axis, a plurality of curvedvanes positioned in said'inlet duct upstream adjacent to said rotor, said vanes being positioned to direct fluid toward said rotor blades counter to their direction of rotation, said vanes tending to cause an increase in static pressure away from said axis toward the'tip ends of said vanes by centrifugal action which tends to limit the range of volume flow of said fluid, said inlet duct having walls curved convexly toward said axis at said vanes and mean lines curved in axial planes to create a centrifugal pressure toward said axis to oppose said increase in static pressure at said vanes, said vanes and said inlet duct and said hub rim cooperating to'extend the range of volume flow of said fluid through saidrotor passages. V a a I 11. In combination in a compressor for raising the pressure of an elastic fluid, a case means comprising an inlet duct, a rotor case and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and defining a flow channel with said rotor case, said channel registering with said inlet and exit ducts to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, and a plurality of peripherally spaced axial flow blades carried on said hub with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exit than at its inlet, the exits of said passages having such direction that with the relative velocity of flow the discharge from said passages is directed primarily transversely of said axis and into said exit duct generally in line-therewith, a plurality of axial flow guide vanes positioned in said inlet duct upstream adjacent to said rotorwith guide vane passages between said vanes, said vanes being positioned to direct fluid counter to the direction of rotation of said rotor blades producing centrifugal pressure in said fluid at the radially outward portions of said vane passages, said inlet duct having its mean line curved in axial planes to be convex to said axis for producing a centrifugal pressure in said fluid toward said axis in said guide vane passages and thereby increasing the volume flow through said vane passages, said hub having a concave rim whose exit end is nearer than the inlet end thereof to said axis to produce a centrifugal pressure in said fluid in said rotor passages opposing centrifugal pressure from rotation of said rotor to induce a greater volume flow through said rotor, said rotor and said guide vanes cooperating with said inlet duct to pump a large range of volume of fluid per revolution of said rotor through said compressor with a limited range of angles of incidence for said rotor blades. 7

12. In combination ina compressor for raising the pressure of an elastic fluid, a case means comprising an inlet duct, a rotor case and an exit duct, a rotor hub mounted in said rotor case for rotation about an axis and'defining a flow channel with said rotor case, said channel registering with said inlet and exit ducts to conduct a flow of fluid, said exit duct being constructed to discharge said fluid transversely to said axis, and a plurality of peripherally spaced axial flow blades carried on said hub with rotor flow passages between said blades, said blades increasing rearward in radial depth providing each said passage with a greater cross sectional area and radial depth at its exitthan at its inlet, the exits of said passages having such direction that with the relative velocityofflow the discharge-from said passages is directed primarily transversely of said axis and into said exitduct generally in line therewith, a plurality of axial flow guide vanes positioned in saidinlet duct'upstream adjacent to said rotor with guide vane passages between said vanes, said vanesbeing positioned to direct fluid counter to the direction of rotation of said rotor blades producing centrifugal pressure in said fluid at the radially outward portions of said vane passages, said inlet duct having its mean line curved in axial planes to be convex to said axis for producing a centrifugal pressure in said fluid toward said axis in said guide vane passages and thereby increasing the volume flow through said vane passages, said hub having a rim converging downstream toward said axis with the exit end thereof nearer than the inlet end thereof to said axis to produce a pressure in said fluid in said rotor passages opposing centrifugal pressure from rotation of said rotor to induce a greater volume flow through said rotor, said rotor and said guide vanes cooperating with said inlet duct to pump a large range of volume of fluid per revolution of said rotor through said compressor with a limited range of angles of incidence for said rotor blades.

814,804 Rateau Mar. 13, 1906 14 Tedman Nov. 5, 1929 Stalker Mar. 16, 1943 Szydlowski Mar. 19, 1946 Redding Feb. 3, 1948 Benson Feb. 17, 1948 Aue Sept. 2, 1952 Davidson Dec. 30, 1952 Wosika Feb. 17, 1953 Kantrowitz Feb. 17, 1953 Stalker Aug. 25, 1953 Price Nov. 17,1953

FOREIGN PATENTS Germany May 8, 1923 Germany Aug. 29, 1942 France Sept. 24, 1952 France Feb. 26, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noa 2355,746 October ll 1960 Edward Aa Stalker It is hereby certified that error appears in the printed specification of the above numb ered patent requiring correction and that the said Letters Patent should read as corrected below.

' I tock column 4L Column 3 line 49 for "rock" read s D lines 60 and 31, for "rnagniture" read magnitude ,fcolulrlrlutzafi line 51 for "R read R column 6,, llne 24, or read than =4,

Signed and sealed this llth day of April 1961a Attesting Ofi'icer ttest:

Acting Commissioner of Patents 

